Thanks to everyone who's been following the story. Here she is, in more-or-less final form. Couldn't resist the call of green. I have to find the right place to add the mandatory touch of red. It's even got a cupholder.
Just in case anyone's searching for this in the future: quadricycle, velomobile, homebuilt, diy, recumbent. That ought to cover it. I'll try to get some videos uploaded soon.